HORSHAM, PA (May 20, 1998) -- Cell Pathways, Inc. today announced results from an
open-label extension study of the company's lead investigational compound,
FGN-1--(exisulind), in patients with Familial Adenomatous Polyposis (FAP; also
known as Adenomatous Polyposis Coli, APC). Eighteen patients continuing on FGN-1
for as long as 18 months following the completion of a six month Phase I/II
dose-ranging, safety and efficacy trial tolerated drug treatment well. The
progressive increase in precancerous polyps that normally occurs in this patient
population appeared to be arrested by the treatment. In addition, existing
polyps in the FGN-1 treated patients appeared to decrease in size or remain
stable over time.

The extension study results will be presented today at the American
Gastroenterological Association meeting in New Orleans, Louisiana by clinical
investigator, Rosalind van Stolk, M.D. of the Cleveland Clinic Foundation.

"FAP patients have historically experienced, on average, a significant increase
in the number of precancerous polyps that develop in their rectum over a 12
month period," said Dr. van Stolk. "In contrast, we observed that new polyp
formation halted in all patients receiving effective doses of FGN-1 for periods
of 12 to 24 months, and in 16/18 patients, small polyps (6 mm or less) tended to
regress in size while larger polyps remained stable."

"We are very encouraged by these results, which show a strong trend that
supports FGN-1's ability to prevent the normal progression of disease in
patients with FAP," said Rifat Pamukcu, M.D., chief scientific officer and
senior vice president of research and development at Cell Pathways. "Left
untreated, FAP patients invariably develop colon cancer." He noted that a
randomized, placebo-controlled Phase III trial of FGN-1 in FAP patients was
ongoing and expected to conclude in early 1999.

FAP and Colon Cancer

Colonic adenomatous polyps are known to precede the formation of colorectal
cancers. Individuals with FAP, an inherited condition, form hundreds to
thousands of polyps in the colon and rectum, and face the inevitable development
of colon cancer from these polyps if the colon is not removed. After removal of
the colon, FAP patients are closely monitored throughout their lifetimes to
detect and surgically remove most precancerous polyps and any cancerous lesions
that may develop in the gastrointestinal tract. Approximately 25,000 - 50,000
individuals in the United States suffer from FAP, with a similar incidence of
the disease in Europe and Japan. Precancerous colon polyps, histologically and
genetically indistinguishable from the polyps of FAP, also occur "sporadically,"
but repeatedly, in more than 30% of people in the United States over the age of
50, putting these individuals at significantly increased risk of colon cancer.

Extension Study Design

All patients completing at least six-months in an open-label Phase I/II trial of
FGN-1 at oral doses ranging from 400 to 800 mg/day participated in the extension
study. In that follow-on study, patients initially received a total of either
600 mg or 800 mg/day FGN-1, with the 800 mg/day group subsequently reduced to
600 mg/day when investigators determined that dosage to be the maximum
tolerated. Investigators recorded the serial polyp counts and the percent of
flattened or haloed lesions in the patient's rectums at 6 months, 9 months, 12
months, 18 months and 24 months.

FGN-1 (Exisulind)

Cell Pathways is developing FGN-1 (exisulind) as an agent for the prevention of
cancer. The orally active drug acts through a unique mechanism to induce
selective apoptosis, or programmed cell death, in precancerous and cancerous
cells without affecting normal cells.

Cell Pathways Inc. has begun or plans to initiate clinical trials of FGN-1 in
1998 in seven clinical indications. The company is conducting an ongoing pivotal
Phase III trial for the treatment of FAP (APC). In December 1997, the company
initiated Phase II/III trials of FGN-1 for the treatment of sporadic adenomatous
colonic polyps and for the prevention of prostate cancer recurrence. A pilot
study of FGN-1 for the treatment of lung cancer also began at that time. In
addition, the company initiated a Phase II/III trial of FGN-1 for the prevention
of breast cancer recurrence in February 1998. CPI also plans to begin two
additional Phase II trials in precancerous indications in 1998.

Cell Pathways, Inc. is a pharmaceutical company focused on the development and
commercialization of products to prevent and treat cancer.

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